This invention relates to contour projectors, and more particularly to a simplified mirror system for such projectors.
In its simplest form, the typical horizontal contour projector consists of a light source, a magnification lens system, a single mirror onto which an image of a workpiece is projected or directed by the lens system, and a projection screen onto the rear surface of which the image is projected by reflection from the mirror. When a workpiece is interposed between the light source and the magnification lens system, a profile of the workpiece is projected onto the face of the mirror, and is reflected therefrom onto the back of the projection screen for observance by a person standing in front of the screen. A major problem with this type of contour projector, however, is that the observed image is upside down and reversed (left to right) with respect to the face or surface of the workpiece onto which the light source is directed. This makes it very difficult for the operator of the projector to interpret the image and to manipulate the object in a desired manner.
There are several ways to erect the image which is projected by the above-noted system onto the projection screen. One way, which often is employed in telescopes, is to utilize a so-called Poro prism system wherein two spaced prisms are disposed at right angles to each other, and are interposed between the above-noted magnification lens and single mirror. The Poro prism system which embodies four different reflecting surfaces, would then project onto the mirror, and from the mirror to the back of the projection screen, an upright and unreversed image of the workpiece. The disadvantage of using the two Poro prisms is that it introduces four extra reflecting surfaces, thereby requiring expensive additional components, and contributing to undesirable loss of light. Instead of using prisms, the above-noted four extra reflecting surfaces could, of course, be in the form of four separate, front-surface mirrors.
A second approach is to include a second mirror interposed between the magnification lens and the screen, in which case the two mirrors would be mounted in intersecting, right angular planes, so that the image from the magnification lens system would be directed onto one surface of the two mirrors, and would be reflected from that surface to the surface of the second mirror, which in turn would reflect the image onto the rear of the projection screen. The problem with this approach is that while this inverts the image so that it is upright compared to the workpiece, it nevertheless produces a reversed image in which the left side of the workpiece is shown at the right side of the image and vice versa. A reversal of the image could be corrected by substituting for one of these two mirrors an Amici prism, or an equivalent roof mirror system. Although this reduces the total number of reflecting surfaces, as compared to the use of the above-noted Poro prism system, a roof arrangement is difficult to produce, and any angular errors are enhanced. Moreover, there is a seam in the image where the roof peak intersects the light beam. The introduction of any such seam in the image is very objectionable in a gaging application.
Instead of using a simplified mirror system, most conventional contour projectors utilize a series of mirrors in combination with several series of relay lenses, which enable projection of an image along a series of axes lying in a common plane. The U.S. Pat. No. 4,223,986, for example, employs in one embodiment of a contour projector three mirrors and a combination of relay lenses for projecting onto a screen an upright and unreversed contour image of a workpiece. However, not only are a number of relay lenses required to effect the desired projection, but the transmission of the image in a common plane requires the use of larger equipment to produce the upright and unreversed contour image.
It is an object of this invention, therefore, to provide for contour projectors of the type described an improved, simplified mirror system which obviates the above-noted problems, and which requires the use of only three mirrors for projecting onto a projection screen an upright and unreversed image of a workpiece, and without the introduction of any undesirable seams in the image.
Still another object of this invention is to provide for contour projectors of the type described an improved, simplified mirror system which eliminates the need to employ relay lenses with the mirrors.
A still further object of this invention is to provide a contour projector mirror system which, in essence, forms the elements of a corner-cube reflector having three mutually perpendicular reflective surfaces, and whereby the beam is contained on each mirror without encountering any of their intersections.
Other objects of this invention would be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawings.